The present disclosure relates to sectional overhead doors such as garage doors and the like and specifically to operating systems and methods for such doors. It finds particular application in conjunction with a sliding sectional overhead door which utilizes a pair of rodless fluid cylinders for mechanically opening and closing a door without the assistance of a counterbalance mechanism, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Overhead doors are known to include a plurality of door panels that are hingedly connected to each other and slidably mounted to a track assembly positioned adjacent a building opening. Overhead garage doors generally include a counterbalance mechanism to assist in the operation of the door. A common counterbalance mechanism includes a torsion spring positioned about an axis for storing energy during door operation so that energy can be extracted or stored during the opening or closing of the door. Generally, during door opening, most of the energy for lifting the door is derived from the energy stored in the spring or counterweight mechanism so that the energy required to open the door is reduced.
Conventional overhead doors of this nature are actuated by a pulley assembly having a cable which is wound around a drum that is axially driven by the torsion spring with the drum being rotated by a chain driven sprocket. The chain is generally driven by an electric motor, pneumatic cylinder or some other automatic mechanism. However, it would be desirable to utilize a garage door operator mechanism with a reduced number of moving parts as such a mechanism requires less maintenance.
Also, when such doors go through a high volume of cycles, such as in a car wash application, the chains, torsion springs, sprockets, electrical motors, and the like wear out at a fairly rapid rate and result in frequent breakdowns of the door opening mechanism. Malfunctions of the door operating mechanism can sometimes also lead to damage to the upper portion of the door which can be fairly expensive to repair. Moreover, corrosive chemicals and humidity may, over time, damage the moving parts of the door assembly further causing failure or maintenance issues.
There are many other types of garage door operating systems such as standard lift, vertical lift and low headroom operating systems having similar features that employ counterbalance mechanisms and are at an increased risk of breakdown, hazard to personnel, and damage to the door when used in a humid environment or in an environment that experiences a high volume of operations. Therefore, there remains a need for a sectional overhead door operating system which does not employ a counterweight or counterbalance mechanism.